1. Field of the Invention
This invention relates to a plunger assembly of the type used in a glass container forming machine of the individual section (I.S.) type when used to produce containers according to the narrow neck press and blow (NNPB) process.
2. Description of the Prior Art
Production of glass containers on an I.S. machine by the NNPB process is generally described in U.S. Pat. No. 5,707,414 (Leidy), which is assigned to the assignee of this application, the disclosure of which is incorporated by reference herein. In conventional NNPB glass container manufacturing, container preforms, which are often called parisons or blanks, are formed from gobs of molten glass in blank molds of an I.S. machine by pressing, by a reciprocating plunger that is powered by a pneumatic cylinder, and this process, conventionally, requires that the plunger and cylinder rod elements of the plunger assembly be separate pieces. These separate pieces conventionally are removably joined to one another by a specially designed threaded fastener that is used to join plunger and cylinder rod clips to one another. Such threaded fasteners, when new, tend to work loose, and, when old, tend to fuse to one another by rusting that occurs in the inherently high temperature environment of a glass container forming machine. Further, a typical plunger is internally air cooled by way of an air inlet pipe that extends into the plunger through the plunger cylinder rod, and this air inlet pipe is subject to breakage in use in the region of the free or distal end of the plunger because of misalignment that can occur in service between the plunger and the plunger cylinder.
The misalignment of the plunger and the air inlet tube contained therein can also lead to contact between the tip of the air inlet tube and the inside of the plunger, and this can lead to an undesirable non-uniform temperature condition on the interior of the plunger.
An alternative glass container forming machine plunger assembly is described in U.S. Pat. No. 3,314,775 (DeShetler et al.), which was assigned to a predecessor of the assignee of the present invention, the disclosure of which is also incorporated by reference herein.